Wal-Mart greeter Betty Dukes is good for a smile and a warm greeting. She's also a woman willing to take a stand against what she believes to be discrimination.

As the first "named plaintiff" in Dukes v. Wal-Mart, the ordained Baptist minister also is the face of the largest gender bias class action lawsuit in U.S. history — one that could cost the world's largest private employer billions.

Her dual roles have turned her into a civil rights crusader for the company's many critics, who have dubbed the legal battle "Betty v. Goliath." It is a far cry from where Dukes expected to be when she enthusiastically accepted an offer in 1994 to work the cash registers part-time for $5 an hour. She dreamed of turning around a hard life by advancing, through work and determination, into Wal-Mart corporate management.

"I was focused on Wal-Mart's aggressive customer service," Dukes said in an interview during her lunch break, after first saying grace over a meal of fast-food hamburgers and chicken nuggets. "I wanted to advance. I wanted to make that money."

But by 1999, her plans were in tatters. Several years of little advancement and frustration with her role culminated with an ugly spat with managers that resulted in a humiliating demotion and a pay cut, she said.

That also became the genesis of the federal class action lawsuit U.S. District Court Judge Martin Jenkins called "historic" while he was handling the case. On Monday, the 9th Circuit U.S. Court of Appeals upheld Jenkins' decision allowing the case to go to trial as a class action on behalf of as many as 1 million former and current female Wal-Mart employees.